No. 9. 



THURBERIA ARKANSANA Bentham. 



Plant annual. 



Rootstock none. Eoots very slender. 



Culms erect, simple or branching from the base, slender, commonly 9 to 18 

 inches high, sometimes depauperate, glabrous. 



Leaves of the stem 3 to 5; sheaths contiguous, glabrous or sparingly villous, 

 the margin villous-ciliate; blade flat, 1 to 4 inches long, 1 to 2 lines broad, flaccid, 

 scabrous, and usually sparingly minutely villous-pubescent; ligule about & line 

 long, the apex narrowly fringed. 



Inflorescence a panicle at first partly sheathed, finally pedunculate, 3 to 

 inches long; branches slender, seldom exceeding 1 inch in length; spikelets borne 

 singly on pedicels 1+ lines long or shorter. 



Spikelets linear, H to 2 lines long (exclusive of the awn), nearly terete, jointed 

 to the pedicel below the glumes. 



Glumes 3; first and second of equal length, similar, lanceolate, acute, green, 

 nerveless or obsoletely 3-nerved, scabrous-pubescent without, apices slightly sep- 

 arated; third (flowering) not green except the 3 nerves, glabrous, rather thick, 

 lanceolate, folded and compressed, awned on the back a little below the apex ; apex 

 cleft half-way to the origin of the awn; awn slender, i to ^ inch long, little twisted, 

 abruptly bent at the middle. 



Flower single, hermaphrodite; rachilla prolonged above the flower (!) into 

 a minute filiform rudiment about i line long, naked or surmounted by a minute 

 scale; palet very thin, hyaline, narrowly linear, 2-nerved; lodicules 2, about $ line 

 long; stamens 3, anther oblong, about i line long; stigmas cylindrical, on short 

 distant styles. 



Grain linear-oblong, remaining closed within the glumes, the spikelet disartic- 

 ulating below them. 



Plate IX; a, first (on the left) and second glumes; b, flowering glume and 

 flower. The rudimentary prolongation of the rachilla shown in b is usually twice 

 as long and is inserted at a point on the axis near the middle of the base of the 

 palet, not on the flowering glume, as shown in the figure. 



